The effect of temperature on the activity of pectinase.

The effect of temperature on the activity of pectinase

Plan

Aim: - To investigate how temperature affects the rate of reaction of pectinase on its substrate apple fruit pulp.

Introduction: -

Enzymes are proteins that catalyze reactions in biological systems by reducing the activation energy needed for any given reaction. They do this by temporary binding to one or more reactants of the reaction they catalyze. By doing so, they lower the amount of activation energy needed and thus speed up the reaction. The activation energy is the amount of energy needed for molecules to react when they collide. The fact that molecules need to collide in order to react is known as the collision theory.

Most enzymes are simple globular proteins, and the tertiary structure of the enzyme protein is well developed. Enzymes are specific which means a particular enzyme only works on one substance known as its substrate. The precise folding of the polypeptide chains ensures that each globular protein has its own 3D shape or confirmation. Substrates bind with an enzyme at a specific spot on the enzyme called the active site. The combination of an enzyme with its substrate is known as the enzyme-substrate complex. This formation is explained by two theories. The Lock and Key hypothesis suggests that the substrate fits into the active site like a “lock and key” where the substrate is the lock and the enzyme is the key. The Induced Fit theory suggests that the shape of the active site changes shape when the substrate molecule attaches to it.

Pectins are large polysaccharide molecules, made up (mainly) of chains of several hundred-galacturonic acid residues, and they are found in plant cell walls. Pectin is able to form jellies (e.g. jam) but in fruit juices and other liquids it is undesirable. Pectinases are enzymes that break down complex pectin molecules to shorter molecules of galacturonic acid, as pectinase causes the disintegration of the cell wall, and so allowing the cell sap (juice) to flow out. This is why the biggest industrial use for pectinases is in the extraction and clarification of fruit juices; as some fruit juices e.g. apple juice may have bits of apple in it. This is where pectinase is used to catalyze the breakdown of the solid apple bits into apple juice, thus clarifying the apple juice. Pectinases are obtainable from fungi, such as species of Aspergillus and Penicillium, and also from bacterial organisms.

Temperature has a complex effect on enzyme activity. The “optimum temperature” of an enzyme is the temperature in which the enzyme functions most efficient. An increase in temperature below the optimum results in an increase in the kinetic energy of enzymes. This leads to higher efficiency of enzyme-substrate complex formation; therefore a higher rate of reaction. It differs in each enzyme, depending on its nature and structure. At extreme temperatures above the optimum, the increased kinetic energy disrupts the bonds holding the active site; the enzyme is unstable and the shape of its active site changes. This means that the enzyme is less efficient and successful at enzyme-substrate complex formation. The enzyme is said to be denatured; it has lost its ability to catalyze reactions.

Effect of temperature on rate of reaction

Hypothesis: -

As temperature of pectinase rises, the rate of reaction will rise till 40°C. As it rises above 40°C the rate of reaction falls.

The rate of reaction will increase as the temperature of pectinase increases because kinetic energy of pectinase increases, thus it moves faster and it is more likely to collide with apple fruit pulp. This results in a greater frequency of collisions. This will result in the rate of reaction increasing. Pectinase works best within ...